(a) Field of the Invention
The present invention relates to a parabolic antenna used for receiving satellite broadcasting and a process for manufacturing the same.
(b) Description of the Prior Art
Typically the main body of a conventional parabolic antenna is manufactured by a sheet molding compound (SMC) method using fiber reinforced plastics (FRP). Specifically, the SMC method includes inserting into a mold a metal mesh which serves as a radio-reflecting member, putting thereon a glass fiber reinforced polyester resin sheet and applying heat and pressure thereto by a press and thereby form a specified shape. Thereafter, a protective coat is applied onto the mesh surface for commercial use.
However, the production process by SMC method is complicated and requires a long time period for processing, thereby rendering it unsuitable for mass-production. The obtained product is heavy in weight due to large specific gravity, resulting in an increased likelihood that the product will fall at the time of installment or during a storm.
In recent years, a main body of a parabolic antenna has been sold which has been manufactured by injection molding using a thermoplastic resin. However, the thermoplastic resin used as a material is low in modulus of elasticity which can cause deformation by the wind. This raises a problem of increasing profile irregularities on the radio-reflecting surface and decreasing reflecting properties. Accordingly, the main body should be made thick, which entails various disadvantages of requiring a long period of molding time, increasing manufacturing cost, rendering the product heavy or the like.
In view of these problems, another prior art product is manufactured by a foam molding or by using thermoplastic resin reinforced with short fiber glass for accomplishing weight-saving. However, such a product is unsatisfactory in mechanical strength. In other words, weight-saving with a thin body cannot be accomplished. The radio-reflecting member, except for those manufactured by FRP utilizes conductive coating. Such a radio-reflecting member varies in reflectivity depending upon the thickness of the coating. Consequently, there remains the unsolved at present about problem of uneven quality of the products, insufficient bonding strength of the conductive coating, and the occurrence of debonding due to shock against the coating surface.
The present invention has been accomplished in view of the above-mentioned problems, and aims to provide a parabolic antenna which is inexpensive to produce, light-weight and excellent in weather resistance and also provide a process for manufacturing the same.